NEW YORK (Reuters) - The Oscar-nominated documentary "The Gatekeepers" focuses on Israel, but its director says that all countries can gain insight about the risks that arise if secretive security agencies operate without adequate restraints.

In "The Gatekeepers," six former heads of Israeli internal security and intelligence agency Shin Bet reflect on their failures and successes in gathering information on state enemies, orchestrating secret operations and tracking militants. They also offer some unexpected perspectives on the Israeli-Palestinian conflict.

"I found myself more attracted to those who doubt, those who ask themselves questions," director Dror Moreh told Reuters. "I am always afraid of people who don't have questions, who don't doubt."

The English- and Hebrew-language film opened in New York and Los Angeles on Friday, and premieres in the UK in April, following a brief run at the end of 2012 that qualified it for its Oscar nomination for best documentary feature.

The film will compete at the February 24 Oscar ceremony with "5 Broken Cameras," a view of the Middle East conflict seen through Palestinian eyes, AIDS documentary "How to Survive a Plague," military rape film "The Invisible War," and "Searching for Sugar Man" about a U.S. folk singer who becomes a South African pop icon.

Beginning with Avraham Shalom, who oversaw the Shin Bet from 1980 to 1986, "The Gatekeepers" covers the period through Yuval Diskin, whose tenure ended in 2011.

The former security chiefs discuss events such as the agency-ordered killing of two Palestinian bus hijackers, a plot by Jewish extremists to blow up the Dome of the Rock shrine in Jerusalem, the 1995 assassination of Prime Minister Yitzhak Rabin, and the role the agency plays in the Israeli-Palestinian conflict.

DEFINING TORTURE

Always present is a struggle to balance security with ethics and politics, and several of the men discuss the scandals the agency faced over the use of what Shin Bet terms "exceptional practices" in interrogations.

Moreh draws parallels between Israel's debates about ethical security practices and the United States' struggle to define torture and regulate its own practices in its war on terrorism.

"I think at the end of the day any organization that has so much power like those clandestine organizations - Shin Bet, CIA, FBI, Mossad - has to have the law above it giving guidelines," he said.

"When there was no oversight of the judicial system on those organizations, they acted as if there was no law, in terms of interrogating people, torturing, killing."

He blames what he calls murky or non-existent regulations for practices that have sparked public anger worldwide, from the use of waterboarding to the abuse of prisoners by American soldiers at Iraq's Abu Ghraib prison.

"They were stupid Americans who the system gave absolute power over other human beings," Moreh said. "They weren't trained to deal with that, they weren't trained in interrogating, and this is what led to what happened in Abu Ghraib."

The former security chiefs' reflections are a mixture of affirmation and regret, but all six agree that the only way for their country to achieve peace is to work with Palestinians instead of against them.

They criticize Israeli politicians for turning a blind eye to settlements in occupied Palestinian territory, and for sometimes dealing lightly with Jewish extremists.

Ami Ayalon, who headed Shin Bet from 1996 to 2000, summed up their collective thoughts, saying, "We win every battle, but lose the war."

Moreh believes that solving the Israeli-Palestinian conflict is the most important issue facing Israel and hopes U.S. President Barack Obama will take a more active role in diplomatic efforts in his second term.

"I think this is like two kindergarten children - the Palestinians and the Israelis - who need the kindergarten caretaker to help them," he said. "They need a grown-up to tell them, ‘Enough! Israel, Palestine, this is what you need to do, do it.'"